In linguistics this is called a coarticulatory effect, and it’s caused by needing to move the articulators between two positions rapidly. As such, it can be thought of as a kind of “hardware” limitation of humans, as opposed to a “software” limitation of any single language. Whether other languages would have the same sounds in sequence is the main factor.

The “ch” affricate (which is t͡ʃ in the IPA) is a mix of a voiceless alveolar stop component and a post-alveolar fricative component. Because “y” is palatal, you end up getting that post-alveolar fricative component through coarticulation.

Edit: here’s an explanation without the jargon:

• “t” in English is produced by your tongue contacting the ridge behind your top teeth.

• “y” in this context is produced with the tongue sitting near the palate (significantly behind the ridge used for “t”).

• The English “ch” sound is actually a mix of two sounds: “t” and “sh”, in rapid succession.

• The “sh” sound is produced between the places where “t” and “y” are produced.

So, if you have a “t” and a “y” in quick succession, your tongue has to move quickly between a couple different spots – and crucially, through the spot which produces “sh”:

“t” -> “sh” -> “y”

And because “t” + “sh” equals “ch”, you get the “ch” when producing this sequence. You can of course articulate things carefully and not produce it – but in common, quick speech, that’s why it shows up. Singing isn’t different from speech in this regard.

This is called connected speech, I think your specific examples would be assimilation where two sounds blend together. There are lots of other sub-topics of connected speech too. I’m sure this pops up in most other languages as well because if you natively speak a language, it’s likely that you’ll naturally find yourself connecting words and sounds. Great question, reading up about this was interesting.

In British English, we do this a lot with ‘u’ sounds. For example, in London we take the Tube, which Americans pronounce ‘toob’ and we pronounce ‘choob’. Strangely enough, almost all English speakers do this with the word ‘train’ and other ‘tr’ words without even knowing it: the first sound is not ‘t’, it’s ‘ch’.

Both British and American English speakers do something similar with ‘s’. For example, ‘issue’ is pronounced ‘ishoo’ except by people with very strong RP accents (that is, posh people), who say ‘iss-yoo’.

It’s a similar phenomenon to the ‘c’ before ‘i’ and ‘e’ transforming into ‘s’, e.g., in ‘science’, ‘ceiling’ and probably hundreds of other words (‘cœliac’ is a particular favourite). Italians do something similar, but they make it ‘ch’ as in ‘ciao’.

Brazilian Portuguese speakers change ‘t’ and ‘d’ to ‘ch’ and ‘j’ respectively before ‘i’ and ‘e’ sounds. For example, the word ‘de’ meaning ‘of/from’ is pronounced more like ‘juh’. In Portugal, though, they use a hard ‘d’.

So, in summary, ‘e/i’ and ‘u’ sounds all have a tendency to transform the preceding consonant, especially if that consonant is ‘t’, ‘s’, ‘c/k’ or ‘d’, more rarely with ‘j’ and ‘z’ and sometimes with ‘b’. If and how they change varies by language and dialect.

(Note: I’d have done this with IPA but I’m not sure about Lemmy’s support for it and I didn’t want to type it all out and have it be a load of non-loading characters, hence my approximations of the pronunciations. Apologies to any linguists out there!)

Dr Geoff Lindsey has a fantastic video on the related phenomenon of why the <t> in statue is pronounced like a “ch” and why English people pronounce tube as *“choob”

In French we have liaisons, where in basically every word ending with an s followed by a word starting with a vowel, the s is pronounced “z”. For instance, mes amis (my friends) is pronounced “mez amis” instead of “meh amis”, des oiseaux (some birds) is “dez oiseaux” and not “deh oiseaux”. One of the many things that makes French hard to learn for foreigners.

It’s called Yod-Coalescence:

https://en.wikipedia.org/wiki/Phonological_history_of_English_consonant_clusters#Yod-coalescence

It happens to other words in English, in some dialects more than others.

Something similar in German is if a verb ends with “st” followed by “du” (you), it’s squashed down to “-stu” …

from a song “Sag mal, weinst du oder ist das der Regen…” becomes “weinstu”

“hast du” …“hastu”

In Scottish gaelic the leading T which is grammically applied under certain circumstances changes the sound of word.

Uisge (water) goes from an oosh-gah sound to a toosh-gah when you say An t-uisge (the rain).

Same with chick, which is Isean (ish anne) to T-isean which is the chick (tish ann).

Definite articles confuse me.

In general in Gaelic many words get smooshed together when spoken. You dont usually say agus (and) youd say 'S which blends words together.

Thats common in many languages. As a native speaker i do not pronounce all my words individually, they often blur together, changing the sounds.

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You mean that sometimes certain words sound like other words? No, that is uniquely to the english language! /sarcasm

This isn’t just in songs, it’s in regular speech too.

Spanish has a lot of connected speech features, too. Especially with words that start with open vowel sounds, since most Spanish words also have open vowels at the end. Example, “Mijo/Mija” (term of endearment for your kid) comes from shortening “mi hijo/hija” (my son/my daughter). There are like 100 other examples I’m forgetting and my spelling is probably wrong since my Spanish is quite rusty but you get the idea

It happens in mine with the same combination of sounds, a case of iotation. Many words which have a “ch” sound in them arose as contractions of “t-y” or “k-y”, which we write as “ć” and “č” respectively.

Did you eat = jeet